The process products find use, inter alia, as intermediates in the preparation of fuel additives (U.S. Pat. No. 3,275,554; DE-A-21 25 039 and DE-A-36 11 230), surfactants, medicaments and crop protectants, hardeners for epoxy resins, catalysts for polyurethanes, intermediates for preparing quaternary ammonium compounds, plasticizers, corrosion inhibitors, synthetic resins, ion exchangers, textile assistants, dyes, vulcanization accelerants and/or emulsifiers.
WO 06/069673 A1 (BASF AG) relates to a process for direct amination of hydrocarbons (e.g. benzene), to catalysts which are used in the direct amination and to a process for preparing these catalysts.
In the catalysts, the following metals or metal combinations are preferred: Ni, Co, Mn, Fe, Ru, Ag and/or Cu (cf. page 4, lines 10-14).
EP 382 049 A1 (BASF AG) discloses catalysts which comprise oxygen-containing zirconium, copper, cobalt and nickel compounds, and processes for the hydrogenating amination of alcohols. The preferred zirconium oxide content of these catalysts is from 70 to 80% by weight (loc. cit.: page 2, last paragraph; page 3, 3rd paragraph; examples). Although these catalysts feature good activity and selectivity, they exhibit lifetimes in need of improvement.
EP 963 975 A1 and EP 1 106 600 A2 (both BASF AG) describe processes for preparing amines from, respectively, alcohols and aldehydes or ketones, and nitrogen compounds using a catalyst whose catalytically active composition comprises 22-40% by weight (or 22-45% by weight) of oxygen compounds of zirconium, 1-30% by weight of oxygen compounds of copper and in each case 15-50% by weight (or 5-50% by weight) of oxygen compounds of nickel and cobalt.
WO 03/076386 A and EP 1 431 271 A1 (both BASF AG) also teach catalysts of the abovementioned type for aminations.
WO 03/051508 A1 (Huntsman Petrochemical Corp.) relates to processes for aminating alcohols using specific Cu/Ni/Zr/Sn catalysts which, in a further embodiment, comprise Cr in place of Zr (see page 4, lines 10-16). The catalysts described in this WO application do not comprise any cobalt.
WO 2007/036496 A (BASF AG) describes a process for preparing aminodiglycol (ADG) and morpholine by reacting diethylene glycol (DEG) with ammonia in the presence of a heterogeneous transition metal catalyst, the catalytically active composition of the catalyst, before the treatment with hydrogen, comprising oxygen compounds of aluminum and/or zirconium, copper, nickel and cobalt, and the shaped catalyst body having specific dimensions.
Five patent applications with filing date Jul. 14, 2006 (all BASF AG), file references EP 06117249.0, 06117251.6, 06117253.2, 06117259.9 and 06117243.3 (WO 2008/006750 A, WO 2008/006748 A, WO 2008/006752 A, WO 2008/006749 A, WO 2008/006754 A) relate to particular doped zirconium dioxide-, copper- and nickel-containing catalysts and to their use in processes for preparing an amine by reacting a primary or secondary alcohol, aldehyde and/or ketone with hydrogen and ammonia, a primary or secondary amine.
The catalysts described in applications 06117249.0, 06117251.6, 06117253.2 comprise from 10 to 50% by weight, preferably from 16 to 35% by weight, of Co.
Six parallel European patent applications with the same filing date (all BASF AG) relate to particular zirconium dioxide- and nickel-containing catalysts and to their use in processes for preparing an amine by reacting a primary or secondary alcohol, aldehyde and/or ketone with hydrogen and ammonia or a primary or secondary amine.
When the very active catalysts of the prior art are used, including in particular the catalysts according to EP 963 975 A1 and EP 1 106 600 A2 (see above), there may be an increased tendency to decarbonylation of the carbonyl function (which may have formed as an intermediate) at elevated temperature in the reactants (alcohols, aldehydes, ketones). The formation of methane by hydrogenation of carbon monoxide (CO) leads, owing to the large amount of heat of hydrogenation released, to a “runaway risk”, i.e. an uncontrolled temperature rise in the reactor. When CO is scavenged by amines, methyl-containing secondary components are formed.
In the amination of diethylene glycol (DEG), there is, for example, an increased tendency to form undesired methoxyethanol or methoxyethylamine. Methoxyethanol is toxic, can be removed from morpholine only with difficulty owing to its physical properties and can thus lead to problems with regard to specification and product quality.
In the case of the example of the amination of diethylene glycol (DEG), the “decarbonylation” is viewed in particular as the sum of undesired components (methanol, methoxyethanol, methoxyethylamine, N-methylmorpholine and methoxyethylmorpholine) which are formed from DEG via methoxyethanol according to the reaction network:

The reaction mechanism of the amination of primary or secondary alcohols is assumed to be that the alcohol is initially dehydrogenated to the corresponding aldehyde at a metal site. In this reaction, the copper or else nickel is suspected to be of particular significance as a dehydrogenation component. When aldehydes are used for the amination, this step is not needed.
The aldehyde formed or used can be aminated by reaction with ammonia or primary or secondary amine with elimination of water and subsequent hydrogenation. This condensation of the aldehyde with the abovementioned nitrogen compound is suspected to be catalyzed by acidic sites of the catalyst. In an undesired side reaction, the aldehyde can also be decarbonylated, i.e. in that the aldehyde function is eliminated as CO. The decarbonylation or methanization is suspected to take place at a metallic site. The CO is hydrogenated to methane over the hydrogenation catalyst, so that the methane formation indicates the extent of decarbonylation. The decarbonylation forms the abovementioned undesired by-products, for example methoxyethanol and/or methoxyethylamine in the abovementioned case.
The desired condensation of the aldehyde with ammonia or primary or secondary amine and the undesired decarbonylation of the aldehyde are parallel reactions, of which the desired condensation is suspected to be acid-catalyzed, while the undesired decarbonylation is catalyzed by metallic sites.